In heat exchangers and other equipment that act as water conduits, solids and minerals tend to precipitate and settle therein. These solids may interfere with the water passage through the system and may deteriorate the heat transfer performance in equipment which is designed to transfer heat from one medium to another.
The present invention addresses the problem of removing solids and minerals from heat exchangers in various types of water systems, and for keeping such other equipment and/or its water conduits free of sedimentation of solids and minerals; if not completely free of sedimentation, then a significant reduction thereof may be achieved.
i. For example, in a cooling tower application:
FIG. 1 details a prior art heat exchanger system. A heat exchanger 11 is used to cool down a high temperature fluid; the system may also include a temperature control valve 12.
Water is used to cool the fluid; in the process, the water itself becomes hot and it is required to cool the water down. The water is cooled in a cooling tower 2. In the cooling tower 2, ambient air 21 is used to cool the water, through forced flow using a ventilation system; as part of the water evaporates, the water temperature decreases.
A problem in this method is that ambient air may contain dirt and dust;
The cooling tower 2 acts like a vacuum cleaner and sucks into it dirt from all around the tower. During the water cooling process, the air comes into contact with the water, as illustrated with cold water 22 and suspended dust 23.
The cooling tower 2 may include a cooling water plastic net 24.
Due to the water evaporation process, there are vapors out 25.
FIG. 2 illustrates the problem during the operation of the prior art heat exchanger system, including:
1. The control valve is fully opened 41, dust is suspended
2. The control valve is partially closed 42, sedimentation starts
3. The control valve is fully closed 43, solid parts will drop
4. Scale will be formed between the solid parts, lumps of solids will block the pipe.
In prior art, during normal operation, suspended solids are usually carried by the velocity of the water and may pass without any significant interference and without settling or depositing scale. However, when the flow is reduced by control valves or other control means such as a variable speed drive to the pump, the water velocity is not powerful enough to carry those suspended solids, and a sedimentation process takes place. When the water velocity returns to a full shut-off there is no force to carry those particles and the particles do settle. In these cases, those particles stick to the tubes or pipe lines and turn to be solid lumps where mineral scale starts to form between those solids.
ii. In some cases this problem is considerable, due to the fact that a machine room may be situated below the cooling tower and dirt will arrive to the circulation pipes by gravitation. The cooling system is controlled by a pump velocity controller which can create a situation of stagnant water in the heat exchanger.